Hemelytra

(Gr. hemi, half; elutron, a sheath). The wings of certain Insects, in which the apex of the wing is membranous, whilst the inner portion is chitinous, and resembles the elytron of a beetle.

Hemimetabolic

(Gr. hemi, half; metabole, change). Applied to those Insects which undergo an incomplete metamorphosis.

Hemiptera

(Gr. hemi; and pteron, wing). An order of Insects in which the anterior wings are sometimes "hemelytra." Hermaphrodite (Gr. Hermes, Mercury; Aphrodite, Venus). Possessing the characters of both sexes combined.

Heterocera

(Gr. heteros, diverse; keras, horn). Applied to the Moths amongst the Lepidoptera, on account of the great variety of shape in their antennae.

Heterocercal

(Gr. heteros, diverse; kerkos, tail). Applied to the tail of Fishes when it is unsymmetrical, or composed of two unequal lobes.

Heterogangliate

(Gr. heteros, diverse; gagglion, a knot). Possessing a nervous system in which the ganglia are scattered and unsymmetrical (as in the Mollusca, for example).

Heterogenesis or Heterogeny

(Gr. heteros, diverse; genesis, origin, birth).

The production of living beings without pre-existent living beings

Or, the supposed production of a living being of one kind from a part or the whole of the matter of another living being of a perfectly different kind.

Heteromorphic

(Gr. heteros; morphe, form). Differing in form and shape.

Heterophagi

(Gr. heteros, other; phago, I eat). Applied to Birds the young of which are born in a helpless condition, and require to be fed by the parents for a longer or shorter period.

Heteropoda

(Gr. heteros, diverse; podes, feet). An aberrant group of the Gasteropods, in which the foot is modified so as to form a swimming organ.

Hexapod

(Gr. hexa, six; pons, foot). Possessing six legs; applied to the Insecta.

Hilum

(Lat. hilum, a little thing). A small aperture (as in the gemmules of sponges), or a small depression (as in Noctiluca).

Hirudinea

(Lat. hirudo, a horse-leech). The order of Annelida comprising the Leeches.

Histology

(Gr. histos, a web ; logos, a discourse). The study of the tissues, more especially of the minuter elements of the body.

Holocephali

(Gr. holos, whole; kephale, head). A sub-order of the Elasmobranchii comprising the Chimoerae.

Holometabolic

(Gr. holos, whole; metabole, change). Applied to Insects which undergo a complete metamorphosis.

Holostomata

(Gr. holos, whole ; stoma, mouth). A division of Gasteropodous Molluscs, in which the aperture of the shell is rounded, or "entire." Holothuroidea (Gr. holothourion; and eidos, form). An order of Echinodermata, comprising the Trepangs.

Homocercal

(Gr. homos, same; kerkos, tail). Applied to the tail of Fishes when it is symmetrical, or composed of two equal lobes.